Silver chloride grains or silver halide grains having a high silver chloride content (the silver halide grains mean silver halide grains having a silver chloride content of 50 mol % or more and hereinafter are referred to as high silver chloride grains) are materials well-known in the field of the art and are practically used as light-sensitive materials for printing or photographic printing papers. The increase of the silver chloride content in silver halide grains has a merit in the following points.
(1) Since the solubility of the silver halide grains is increased, the development and the fix are attained in a short time and the light-sensitive materials suitable for rapid processing are obtained.
(2) The absorption in the visible region is reduced (the inherent light sensitivity is reduced) and the separability from the spectrally sensitized region is improved.
On the other hand, silver halide grains having [111] faces mainly as the outer surfaces (hereinafter, the silver halide grains are referred to as [111] type silver halide grains or [111] type grains) are well-known materials in the field of the art and in light-sensitive materials for general photograph, the [111] type silver iodobromide grains are most usually used. In particular, [111] type tabular grains have the advantages that the grains can be effectively spectrally sensitized owing to the large specific surface area (the ratio of the surface area to the volume), the covering power after development is large, etc.
In an ordinary production condition, the high silver chloride grains tend to become grains having the [100) faces as the outer surfaces (hereinafter, the grains are referred to as [100] type grains) and hence for producing the [111] type grains, a specific means is required.
Wey (U.S. Pat. No. 4,399,215) discloses a method for producing high silver chloride tabular grains using ammonia. However, in the case of the tabular grains produced by the method, silver halide grains having a high solubility are produced at a higher solubility owing to the use of ammonia, whereby it is difficult to produce the practically useful small-sized tabular grains. Also, since in the method, pH at the production is high as 8 to 10, the method has a disadvantage that fog is liable to form.
Maskasky (U.S. Pat. No. 5,061,617) discloses high silver chloride {111} type grains produced using a thiocyanate. However, a thiocyanate increases the solubility of silver chloride grains as the case of using ammonia.
Also, for forming the [111] faces as the outer surfaces in high silver chloride grains, a method of adding an additive (a crystal habit controlling agent (i.e., a growth modifier)) at the formation of the silver halide grains are known as shown below.
______________________________________ (U.S. Pat. No.) (Crystal Habit Controlling Agent) (Inventor) ______________________________________ U.S. Pat. No. 4,400,463 Azaindenes + thioether peptizer Maskasky U.S. Pat. No. 4,783,398 Dithiazolidine-2,4-dione Takada U.S. Pat. No. 4,713,323 Aminopyrazolopyrimidine Maskasky U.S. Pat. No. 4,983,508 Bispyridinium salt Ishiguro U.S. Pat. No. 5,185,239 Triaminopyrimidine Maskasky U.S. Pat. No. 5,178,997 7-Azaindol compounds Maskasky U.S. Pat. No. 5,178,998 Xanthine Maskasky JP-A-64-70741 Dyes Nishikawa JP-A-3-212639 Aminothioether Ishiguro JP-A-4-283742 Thiourea derivatives Ishiguro JP-A-4-335632 Triazolium salts Ishiguro ______________________________________
(The term "JP-A" as used herein means as an "unexamined published Japanese patent application").
As described above, various crystal habit controlling agents are disclosed but for producing more preferable high silver chloride tabular grains, the development of new crystal habit controlling agents has been desired.
As the properties required for the crystal habit controlling agents, it is particularly important that the crystal habit controlling agent does not reduce the photographic sensitivity and does not hinder the adsorption of dyes for spectral sensitization. In this point, the use of the azaindenes or the pyrimidines is undesirable.
Furthermore, Maskasky (EP 584817A1) discloses a method of desorbing the crystal habit controlling agent by lowering pH and then exchange-absorbing an oxacarbocyanine dye containing iodine, for keeping the form of [111] tabular grains. However, such the exchange absorption method becomes a large load in the production.